Private branch exchange system



Aug. 24, 1943. I

H. M. B ASCOM ET AL PRIVATE BRANCH EXCHANGE SYSTEM Filed April l1, 1942 6 Sheets-Sheet l H M. AscoM NVE/V70 F R. AMBERTV ATTORNEY Aug. 24, 1943.`

H. M. BAscoM ETAL 2,327,851

PRIVATE BRANCH EXCHANGE SYSTEM Filed April 11, 1942 6 Sheets-Sheet 2 H. M. BAscoM /NVENTORS R. 'LA/awry BVM/JM A TTORNEV Aug 24, 1943. H. M. BASCM ET AL 2,327,851

PRIVATE BRANCH EXCHANGE SYSTEM Filed Aprill ll, 1942 6 Sheets-Sheet 3 /A/l/ENTORS H- M- BASCOM y F LAMBERT? ATTORNEY FIGS Aug. 24, 1943.

H. M. BASCOM ET AL PRIVATE BRANCH EXCHANGE SYSTEM Filed April 1l, 1942 6 Sheets-Sheet 4 /NVE/VTORS EH M BASCOM R. LAMBERTV ug. 24, 1943. H, M. BAscoM ET AL. 2,327,851 I PRIVATE BRANCH EXCHANGE SYSTEM Filed April 1l, 1942 6 Sheets-Sheet 5 H- M. @ASCOM /NVENTORS E R. AMEL-RTV By` g ATTORNEY 24, 1943. H. M. BAscoM ETAL 2,327,851

PRIVATE BRANCH EXCHANGE SYSTEM Filed April 11, 1942 6 Sheets-Sheet 6 L' G8 Qld E3 g J F j jm g; 2555*?(67519 a 1 EL H M. @Asco/14 Nm/70H55 R. LAMBERW vw/JY A7' 7' ORNE Y e aaai," e Faltan BRANCH aXcHANEsYsTEM? ii'eiiiiy' iu".- aaeieiiigiew Yeijk, "eiieipgfefieeiek it,

This invention relatestoi-telephone systems an more particularly tov .automati:j pirivatebrainel'i exehanges: of large capacity employing; a manual Y switchboard 'for (a) answering land ,eitending incoming calls fromacentrfal office' toa Iocal 'e sulesoribets line;` either. dialE *or` rr-ianua'l', ora to completing calls` between a loo tie-line either direction, or? i uals'tations or between a manual-'station an'df adialstation. t Y i ith some cases`wherefan,existingprivtebrach exchange equipienthasal dei-'im eapaoityV and Whosel line' ci-reut-arr'a 'gement vof a certain type,\ t-may" beco greatlylincr'eas'e theiiuinllerv of lines e served beyondrthe maximum capacit-y' of the presit equipment aridi, te avoid lthe necessity' 'i audliiig Y Y extra equipment tothe present line eifelexeiienge ini aider te fiinetipriiii the de maimer, lie present'cireuits hav'erhenfdvlo istatioh and? a 1\) for completing- (omit-27)" ground to cppergifteI the cutyoiin-:thef ne circuit. Suh van ariangeinentwhil'e :employing Y smaller jacks than the board` Vfirst mentioecL' requires aniextra relayper line.`

, in cas'e itis desir'edto substantially increase the number of rlines .in existinglexchangesofthe Y type first mentioned, i. e., a;1'nuch largerfmanual board would he required clue tol ,the .fact that jacks? having auxiliary ground-springe are` re'- quiredwhich auxliaryrsprngs o'ccupy' ,a relatively large space in thev fa'cezof the boardgirands-uch `calls either direction betweentivllocal manff ivi-ieespeeiiieaiiy, United siennes Patent-11174734? i having only tip and'ring springs andswitchboards so equiupedhave; in the past; been limited te Y ojthe order of less.

exchanges having'a capacit than 2,000 lines; i Y f harger private branch exchanges have' 'ee'ii gie- Veloped having` a capacity of thejoiider' .of '5' 00D lines; and the swiiciiboares, used" therewith, have beenaflja'fnge'd' with Circuits'jiji accordance' th United states Patent 1,866,260', tireliiiese'f which terminate' et the manual boaidm siiiaii'er jaeiis 'Y having only tipand ring springs 'asi sloi'nlin Fig. 1v ei' the patent; In uns 'effaiigemeritiewii'i be noted that the jack sleeves ofthe station lines e are connected to' grpuni--imseries with ajsleeye relay which operates When aeplue; is; ineeiid,

fromkba-tfteryonf thiefsleeve of t'h'cfeorfi toVV connect tenietA connectlto ais'ubscribersline whi 1,866,260` in order t'o' serve theincjreased lines;

'which boardeniploys thefsmaller type `of Vjack Circuit used'for the additional new lines.

.The present invention therefore provides? cir"-` of the Ydesired 'large apacityfwhi'eifiz employsthe smaller type; jack', `together with certain relatively inexpensive Ainodificatons' ifi the automatic le'Xi circuits whereby l liset oper-ating ie'atuies' are 'ta' `led adciitioiiar features matie' available without anieteiisive aclii-tions en iliier-eiieuit equipment oifi zany materia l-nofr'ease ini-the' Cost ofthe' additional are required, resilesin Cdnnee'ting' thlineout oifl relay, Vin series, with the'central: o flioe battery? both Athe answering arilY callifigsleetes of thecotl availablean'd furplace of the usual negativelcentralbatterylof the order of 48 volts.

Other features reside in further modifications of certain arrangements of the cord, and of the line, trunk, and automatic switching equipment in which the cord is to be used, which provide the necessaryoperating. functions. of the; sys` Y tem, which features will appearfronr the following description when read in connectionY withthe accompanying drawings:

Fig. 1 of which'shows a dial subscribers line"V appearing in the banks of step-'by-step linennders and connectors and alsoin multiple jacks l located in theiace of an operators s'witchboard;`

Fig, 2 V*shows 'a manual subscriberls line cir cuitalso appearing in jacks at the switchboard.

Fig. 5. shows the line circuit ci 'a central'oiilce trunk.; and,

Figs'. 3,4,k 6 and 7, when arranged in accordance with Fig. 8 show a cord, position, and operatoria telephone circuit, the answering or rear plug 'oflwhich' is' shown, V'for convenience, opposite-Fig. I J

Station to station connection the present invention it will'rb-e first assumed that amanualstationn (Fig. A2) calls and de.-

. corresponding to relay 8 of Fig.` 2 and relays'il and 26 in the calling end of the cordV (Fig. 4)V operate in series in a circuit extending. from negar tive centraloiiice battery, winding of theline f `cut-olic relay, winding of relays I9 and 2li, Aand positive battery Bi to ground. In thisgconnecf tion it is. assumedthat the Aresistance of 4the-cut- Y A 'off relay of the subscriberslinesis of tl'ieo'r'der,y of l200ohms, relays 6 and IS are 100 ohms each- "f, and relays 'l and 2i) are 31 ohms each.v Operation of the cut-off relay in the called line per-lj formsxthe usual .function ofl disconnectingythe' line relay from the'v line and connecting the line j throughto the tip and ring springs Aof the jack.: Operation ,off relay i9 closes anv obvious circuit to operate 'relay 2i, and relay 2i) operatesrelay?. l 22 which latter'relay in operating,` in conjuncf.

f tion with the'previous operation of the answer-rv ing supervisory relay i4 and relay 2i, closes a-.-. circuit to operate'relay 23 which circuit can be traced .fromground, resistance 24, conductor 25,. 1 A Contact 25.0f vrelay 44,. contacts .121; of relay-,36,

f lowerwinding of 'relay 23,' conductor 28, contact Inf-describing vthe Voperation of the` system yoi 25 sires to be connected to a 'similar nianualstationlnot shown), whereupon the' line relay i operates inaJwell-known manner thereby closingits contacts 2 to lightthe line larnp 3 at the switchboard. When the operator answers byinserti'ng the answering plug 4, of her cord circuit VC (Fig. 2), injackf, relays 6 .and l. in the cord sleeve operate in serieswith'cut-of Vrelay 8 vof thefline which circuit can-be traced yfrom Vthe negativepole of central cnice battery Bv (usual.-

` lylfvolts) throughxwinding oirelaySJoverthe sleeve contacts '.of jack 5 and plug 4. and windings jor relays ii andil to the Vpositive side of. the

` V`independent -battery S whose negative -pole' isY connectedV to ground,v The battery 9 isviof relatively.;low potential with respect toy centralcilice batteryB (in practice. ofgtheorder of 6 volts) and'isin series-.aiding relation thereto, and re,d lays 6, 'i and 8 operate.- A A Relay 8 inoperating disccnnectskfthe line'rrelay -i which -in releasing extinguishes themline lamp 3. Relay Sjalso connectshe. lline through tothe tip and ring. of the .answering pluga. of

. thecordcircuit.;r Qperatlon of relay G performs no useful function atithis time but relay?, inv operating,rclos es the circuit for relayA Il) which opens itsv Contact ii.V thereby preventingrelay i2 from operating anoll at its contact i3 closes the 29ofre1ay 2 2, conductors andl3.i,'contactsf32 v of' the nightland through dial key. 33,.ccneluctor 34, and contact 35 of relay ll tobattery. `Relay 23 inioperatingzlocks, through its upperwinding and contactszkunder control of relaysl and.

' 2i in-the followingr circuits;-- Ground, contacts 3 3;V

of key 33, conductor 39, contacts 40, of yrelay vI conductori, contacts Bland upper winding oi lrelay, 23, conductors and 3i,contacts32=o1l. Y3.5 or" relay f key 3,3conductor 34, and-contacts ductor 43 and preventing the operationf retipconductor'of the cord' through'tog'rounclin series withV the rightwindingA of vanswering supervisory relay I4 and the upper winding of re-` v lay i5. f Relay i0 in operating also closes at its contacts ESI to short circuit relay 6 therebyreducing the resistance of the sleeve circuit to a low value.

L Relays i4 and Y.i5 operate in series with the subscribers line. Operation of the supervisory relay I4 opens at another point the circuit for the answering supervisory lamp 'l5 which circuit was partially closed atV Contact il ofV relay it! whenlthat relayoperated. l l. The operator after' receiving the lrequired information v froml the calling station makes theV usual busytestwithf'the tip Vof calling plug .I3 and, 'assuming the Ycalled line'is idle and similar to theline of station A inserts `calling plug i8 (Figa) in" the jack whereupon thecut-oi relay,

. lay-.44whenV relay 2l operates. Operation oreflay 22' lights thecalling supervisory lamp, under 1 control o f relaysd and I6, the circuit forlwhichV .can be traced vfrorngrourvld, resistance 41, vback contacts 4of relay ,46,vv contacts 48 of .relay 49, conductor 5 0, contacts Stof relay ID, conductor 5,2',

contacts 53 o f relay 22, and'l'ampv lieto battery,V

Withv the :foregoing relays in thecord circuit. op-

is appliedetdthefcalled line in seri'esf with .thev upper winding of tripping'relay' 5.6, the circuit for which v can be traced from grounded battery,

when itisin Contact with the vringing segment 5T, contacts 58 of relay. lli,Y conductor 59,'uppe'r through the ringerat the1 called station, back overtlietip of. theline and plugl, contactsiitA of relay,2l, contactsvfof relay' 22,',contacts Gli of ofrelayEi', conductorcontacts 61 oref lay i!! t'o the grounded terminals of batteryli'n' series with the ringing generator. Connected at a point 68 Ybetween the inner lower armatureoi i relay 56 and contacts 6I Vofr relay'22 a circuit ,in series with a condenser'l' extends to the ring conductor of the answering end of'thelc'ord and thence to the calling station as anaudible ring# ing signal. kThis circuit can be traced from the point 68, conductor 69, contacts 'l0 loffrelayV 23,.

conductor 1i, contacts 72 of relay 22, condense;`

`13, and-thence over-contacts of the ringing key f Ilathe night keyY 33, talkV keyV '14, relayflll, con# denser 15, windingoflsupervisory relayY i4, and rear ringing key 16 to the calling line'and thence i reim .wnicn''s inseneswitntne. previeiisiytracee ringing circuit" operates in tlrejusualmanner di'sconnect,` at its conta-cts 6|?, the ringing' current from the called line,and"siiort-circuitsiatitscon;v v

tactil', the condenser fin affcircuitlincluding of relay 3l and conductor 68;'. Closure 'ofc 111-" ccntactsl'l of relay 22, conductor Thcontacts nects the calling endo the cord;tothe'battery 1V ates in seri-eswith the called station' wnojsere ceiver is new off the hook. Operatiurroflr'elay" flfopens its-' contact 19 thereby extinguishing the f callingsupervisory lamp-144 'and byy `closing its contacts 89 causes relay 4:9'- tooperate froinbat!Y tery at contactsl 35 of' relay 21|.' Relaylin' operating Ylocks under `control of relays 83,' 2| 'fand ZEYina circuit which can be traced ffrcmground,

contacts 85 orrelay` 83, contacts 'fancl upper* Winding ci relay 9, contacts 86? cfrela'y 63, ecn# contacts 32M ofV `talk key 33', conductor. 34', and contacts S5` of relay 2| to`- battery. Opera- Vtion of relaye' c'l'osgits contacts'j8f8, Whi'chprepares' av circUitjtO'operate relay 89 -tvhenjr relay 'releases due to tlrecallecl' subscrberreplacirig l his receiver on the hook; j At this point; when the cal-ling and cal-ledfetations 'are interconnected for conversatiori, We

v can 'summarise as? followsz. (00,5 batteryrand groundyfo'r the calling s'tati'onii's supplied inV sie-1 ries `'with relays I4 andl gw)` battery aridground'f for' theca'lled station'is supplied in 'series :wi-thi by interrupter I, torelay IUD which, @perf- Y relay 4S; (c) Vtlreanswering and calling@enfle of` (d) lno bridgev exists acr'o'ss thetip and ring Vcorr-f ductors, of the, cord other tharrth'eringin rela-y' 82 Whichlias noV useful function' at tliig-t i Y j When the calling; subscriber replaces-'liis''r'e-l ceiver cn'tlfie' sw'itclihook; relaysl |13 and. l 5 release.

Relay" |54v in i'releasifiigclosestI itsubacb contacts thereby cor'np'leting.'y a circuit to:oierateVA relay 3 6 which can be .traced from'. grcuridgresistfance 2i conductor `Zar-back Acontact of relay le, cr'intactffi!` of relay'.V 23,` contactlfandcwindin'g at relay` 313,`

If before the?v answering: amdrcalrrlingplug are removed the calling= Jstaticns'aigaire removes his receiver toifrecallthe operator; supervisory relay Mi reels:eratee:therebyv opening its back cerrtfact- 1 arret-closing its-front; contact 2S-:thereby causing. supervisory lamp" t@ Vtofilasln.asagrecalbsignal, Thisarrangement is Well-known and described-ine 20j United States'Patent 1,866,269, see Fig.v ibut can; f

beybriely ,described 4asf fellows; closurgjoffcenw tacts 26er relay' Mfcompl'etee the follo'wnercincuit: battery; low resistance upper` Windiifigel?v is `also` clmnecteel` tabattery thereby establishing. a lou/:resistance (2Q-om) shunt--arcuii'cii the lamp causing-it tol Vbe extinguished;- 1 Relay .98v operates Vin this circuit thereby closing-itscontactsitqpcnf nectf ground, interrupted at la; predetermined'rate ated', openeitsf-contacts S51-,hereby removing: the shunt from. lafm-p lfanqperfr-iitting itto relient.. Relay Jl-Bil. alsoA closesits contactsV l8 2 thereby completing i a-hclol'ing',circutior relayA S'. includ ing itslower-land. high resistance'- v/ i'ndi'n-g. ,l/'lien the interrupter removes groundirorrr relay I'il this relay releases and recloses contacts S`9 'and replaces the shuntaroun'd. lamp |'B 'wli'ch lan is again extir'iguished. "l`lf1is peraton continues anni the. operator actuatesthe taiiilya;

operates Arelay 33 'in anobvius; circuit te er'furdv atcontacts' offth. monitoring; key' F03" (F'gl' 6') Release of; relay83.opensat. its contactsfand 86 the holding-ci'rcuito'rf` relay 3'5" which releases and extinguisnestneiainp. j i Air'ecall' by'tle-calleqsubscriber is eiec't'edf in "the saine `manner"as" previously described bythe 22, conductors. Sti and; 3|., contacts '32: "ofllieyzi, conductor 34 andcontacts 35 of relays2r|Y tobattery. Relay 38' in', operating. lockslo'lver its .conrtacts 92 in. a-'circuitwhich. can' loe.tracedY fromk battery, Contact 35` of. relayzi, conductor 54,

contact. 32 of key 33,. conductorslfand 3B, contacts 29. and 87; oirelay 22t,contact'88 orrrelay, winding and contacts 92i oii'relay 35;. conductor 4|, contact 'of 'relay III,` conductor 39 andzccntacts 38 ckey 33 toground. C

Whenrelay I4. released, the supervisory lamp i5' was lighted' over contacts Il'y of relay' land closure 'of contacts So'f relay 3S; shunted. the back contacts of relay i4 4thereby holding the lar'np lighted under control ofrelaysY |53; and 36.

.l/'lienV the receiver at the called 'staticnis replaced on the switchhmglrV relay releases ausing relay 89' tofoperate umier'cont'rlof' relays 63,

follows: When the trunl'c i'ss'ei'zediat'the central 'roiliic'e, Wliielr We will assumev is arranged' fcrfn'ia'e chine1'ingin g`, groundconnected to the ti'p'durl ing: theer silent interval off the ringing i cyle there Y u 5;, and thermistors'j l is fa-ngi. I i, operates. i A rectier ||8is connected infshuntto therelay Y mitted tothe central oflice.

I 3'. The thermistors I I6, I l'iare devices whichl have` .Y the .characteristic oi rapidly decjreaslirig` in resistance :with vanincrease .in zapplied potential, i. e.at zero` potentialftheyhave anormal highresistance of the o r. lerv of '50,000V to 75,000 ohms and decreasein about one half second to aboi1t- 1,000 ohms whennornialringing Vpotentialj'is applied. The impedance ofrelay- '||3, at

eser/,Sri

Vatingcloses a circuit to operate. relay ,4 4`which1- yt can beV traced "to Vgrc' `1'1n l`,lbackv contactoffrelay 1, contacts |29 of"re1ay'|2,conductor|30 andl l' winding of .relay-.4,4 to battery. Relay 2'fa1so`v closesv its contacts ISI and 13 2 thereby 'connectringing frequency (20 cycles), is so high 'that I ringing current Vapplied to either side ofthe line will not flow through .the respective thermistor to operate thev relayand/therefore the rectier V IIB is connected? in shunt tothisrelay so 'that' one half of each cycle of theringing current will by-pass the relay thereby causing the'respective thermistorszto reduce its-resistance to--a value suchthatit will pass sumcient current. When this occurs Vthe other'half cycle, 'which'v is v notr blocked by vthe rectifier, flows'through the relay ||3`causing its operation'.V The ftherrnisto'r connected tothe opposite side of the line, i. e.. the side which is grounded at the central loice during ringing, is so high in'resistance lcompared' with the resistanceof relay- I I3, vplus the resistance'to battery, that sufficient"ringin'g1current will-flow to ground through relayl I3 to cause its operation.` The reason for providingaleonnection between the relay ||3 and each side 'of the lineis due to the fact that under certain' conditions ringingk current at the central oii'cemay eration'of lrelay 44 disconnectscondensers y'I5 and j 8|v from the" talking circuit vof the cord; discon'.- nects the battery feed relay 5 fromthe tip. .and ringof the. answering cord,.'disconnects thebat 'tery 'feed relay 46 from the'tip andring conduc- Y tors *0f `'the callingfend of the cord, andco'nnects Y vthe tipand ring conductor. of the answering cord directly to the corresponding conductors of the calling cord. c L When relay |28 ofjthe central oice trunk 1 operated, it connected theupp'er andlower iavirid-` ingsl of. relay.|22`in series-between batteryand: vgroundcausing this relay to fully operate which thereupon Ydisconnects its lower windingf'fvr'om the ring of the trunk,rcloses the tipand ring'through' 7 from the jack tothe central oiiice lineyprovides; a separate groundfor holding relay I0 operated, preleases relay ||3,.'and"op ens thecirc'uit'or the..

trunk lamp v|011 `which is thereupon extinguished.; Attlns' point the operator Aactuates thecord circuit", talk key 14, thereby. connecting hertelel-vv phone set y(Fig. '7) to the cord,A andiobt'ain's the number of ,the wanted subsc'riberfwhichwe:will

assume to be subscriber D (Fig. l). whose Ystation be applied to the ring and vvunder certain other conditions to the tip. This arrangementwhich includes the therrnistors` IE6 andlliis'ffor the purpose of preventing/false operationbf relay I I3 on currentreversals which may ccuron the central oiiice line and also to prevent-'thisrelay from operating when ldial pulsesare being trans- While ringing current is 'being"appliedy at the centraloilce, relay |05 remains'nperatedV dueto ground on the tip" conductc'r'rof the trunk, assuming that ringing current is beingapplied to the ring. YWhen relay ||3 `operates Yit locks over its upper Contactin the following circuit: battery, winding and upper contact'of'relay |'I 3, contact H9 of Vrelay |20, contacts I2| of'rela'y |22 and contacts |23 of relay I'IZWhic'hjrelay was oper-UV ated in response to seizure of the trunk" at the `Closure of contacts |24 lights central Cinca trunklamp |04 in an obviousfcircuitY When the'operator answers byfully seating the answering .plug 4in jack |25 sothat contactis made between `the ring of the plug andthering spring of the jack, battery onj` the .ring of the answering plugcauses partial operation of relay D is Wanted tests the sleeve of jack I 38er |39 with,

the tip of plug lin the usual manner.v If.V the f line is idle the'jack sleeve Willrbe at the full negative potential of the centrar ofce battery, ige.)v`r

-is equipped -with avdialand hasaccess to',fand accessible. from, an 'automaticexchange byi'neans y of line nders LF and connector. CON,"respec tively. Subscriber D is also accessible kfrom thel manual switchboard Aby ymeans* 'of multiple. j 'acl-r's line nder of the typel question'v vrThe line circuit forsibscriberD employs aline relay I 3 6 and cut-oirelay'I'ljwhich'perform the usual functions. I

The operator upon ascertain'in'gthat Vsubscriber 4S. volts, which is the same potential sourceas the' batteryV I .ljg connected to 1 thel b'usy-;test; circuit (Fig..7) andtherefore theipotntial at 'bothends' of the lower vleftwindingoftransformer.I||!,lnV the operators telephone circuit, .will be equaland i no click will betheard infthejoperators receiver.

In case; however, the lineisengaged bythe fconf nection of either a line nder or connector there- |22 over its contacts |26 andlowerwindingj which causes its contacts |2*| to close thereby operating relay |28 over thesleeve ofthe cord including relays 6, 1 and the lowlvoltage positivej battery S. The combined resistanceoi.resistance H which vis in series with relay|,2i Y and the winding of relay |23 is suiliciently highlto prevent cord sleeve relay 1, which is marginal, vfrom operating, and due to this fact relay Iii does notoperateunder this condition, i. e.,con

nection of theccord toacentral oince trunk having -a relativelyrhigher resistance sleeve circuit than the sleeve circuit-cfa subscribers line, as previously considered. f Sleeve relay 6, however, foregoing circuit which closesA a.c ircuit, at its from Contacts, ,wwf-frate .relay .H2L/Which. cludes contact II of relay I0. Relay 2 :in, 3pcv1-v to, the sleeve lcircuit will be grounded and a click will be heard-in 'the receiver,A and further the con- :nection of a -plu'g'such as '4 to jack |39,1for example, connects tlie six volt positive battery 9. toV one end ofthe lowersleft winding-'of 'c'oil III which will also produce a click inthe operators receiver.

vIn case the linejfis idle, the operator wil1;in-, sert plug I8 in -one of the multiple jacks l(I38, or |39) of the line lappearing at her position thereby operating cut-'oir relayllfwhich disconnects line relay |36 from the line. n Relay |3 operates ina circuit from negative. 48 voltage battery, winding of relay |31, sleeveV conductor of jacki|38 or |39.

and plug |8"a'r 1d`winding of'relays I9 and20 to the positive terminal of low voltagesix voltbattery, 'thenegative terminal of which is connected to ground. f' Relay I9 operates vrelay 2| which turn opens its contacts |42-therebyV disconnecting. the busy'test ieadg'ma from the tip gof plug; |a`. l

`valso'opens itscontacts |44 thereby'` dis- 'i from the ring ,conductor of ihe cord andtat-thersame time closesits .contacts 162 .and '63 thereby' j" connecting the tip. and ring 4conductors1 of1 the calling cord through to relay 22 Operation of i relay 27B. caused relay 22 `to `operate at 'the same 'time 'as relay |19 and therefore' with `relaysfM rand 1 '22 operated ringing current is .,automatieally ap- I Vplied. t0 the Calledllne. 'i751 v'SeriesWith the upper Winding of relay ES in the following cirouit.

relayY 22,; contacts-65 of relay 56, Ve ond iiutor and contacts Eil'ofrelayl to grouijid.v

stead of operating Vrelay 553,1 relay M ,isf operated dueto the present operated condition Qi-relay 'Whohrelay l) o1l e 1"ates in'serieswiththecentral olice batteryvandtthe A( ialle'd' statienxteiei phone'oircuit,` `Oigeration; ofrelay |13 eausesrelayV 23 to Operate, vthe `circuit `for Whieh'fean Aloe traced from ground;resi stanee 2 6, conduetcir 25;centats Z26 of -relay iii, contactszj'- of `relay 36, lower fyifind-V ing of relay-23;c'oziducter 2 3, contacts `250i; relay tery. Relay E'flooks'under feontrelf o'arelaysjl and IZ and opens itscontaet I Gtherely removing ajshort'cfirc'uit whiehfhad prey-iuslybeen con- .v

netzteilaround-ithefy 859 ohm Vresistance.HVL f By* rerhoyingi this lshort- Circuit the resistance` M1' is ad'dedto f the Vresistance of 'the' retard coily 1| 33 'which 'isf ebnheetedaoressfthetip and ring-cen- Y ducto-rs of the cordwhenebntacts I3|fahd |32 `of Vrelay I2 are closed; AThisinerease-in'resstanoe of the bridgeallowsmore'Currentto'fiow through "thertransniitter fof the'cal'led-subs'criber Di il v Y j W e may new summarize "the reor'iditions of the above Conneetionasg fellows (d) talking battery. fer theealled stationD `is supplied over the trunk .YT andeerd' circuit "C jfrom the central olieefib) a relatiyely high'resistaneeilZOO hms) yconsistingof resistance. |41 andretardooil |33,i n series,-` is bridged aerossthe ltip-.andringeondutonoftlie eordCv; Vandc'll the supervisory relay :I4 isiunde'r controlfofthecalled stationli.:l Y

1 ,Whenzthe receiver'atstationi is `replaced on'v ioY dition.:

" fwhen the called station answers the tripping "relay 5B dperates as' rreriouslydsribed, buifineo identied as `relayf in the beforemntioned :siekeiyfPaient 1399554; and' cause 'the Asii/imiV 4,

ienjimorfa positive poieniiaii (inL thel brush isi Trom'flo'wing through the relay V|53 thus insuring thatitwill not operate underlthe busycon- 1 cord sleeveirelays -werejconneoted to ground `they ,Woii1d.operatey in seriesxyyith Ithe station cut-.off ,relays ,such as-|31 and V|58V onregular cennecf f Y tions butti-i the operator were tovjplu-g intoI a failure ,of relayfl'g, for instancegto operate would preyent'relay 2| fron 1 operating thusyholding i the tip ,.and ring. `conductors of the cord; open ai emmers as, and e2 er 'relay 2 i.V vFarine nain which lights thesupervisory lamp 155associated` i withthe trunk or calling cord Whichis connected therline osubscriber D. This `circuit can be potentialare sixl volts Vpcsitiye ,respect `,to ground VVdueto the low voltage battery 'Blln s'criber, not shown, Whose; line appears' in a higher numbered terminal of the sameline nder bankilevel. as subscriber D, .shouldorignate a eeiver'.V A, Y

Y ABy reason 4series with relay 2 3 in 'the s leevejlcircuitoffthe ealling end of theord.: In caseag `dial-,sillae fca'se .the operator' I disregarded the busy Acondi-- tien and inserted plug .|f8,;into jack I'Syior eX- ,amp'le 'thef tip lef. the `line lwould'fbe -at ground potential.,andV Tal' ,st'eady Y current would ow y"through `the fbusy test (lower` left')'j,.winding 'or .ftrarfisformeri4 l, due tj,c .fi',l'ierfa-*etL 'that'relay 2| j didiil'ot operate and contacts illlzwuld 'there- 4"fore.;remain' closed.4` lIJnder .this eindition iria seeond'` cord should .befused to testfanother. .Whiclilwas idle,.due tothe fact .that-the Vbusy fl test lead 143, 'which is commento 'all ftheoord Y "causing affals'e busy gliele in theV operatorfs ref- IIBI-jin the sleeve circuit of thev plug |3,` .the foregoingr difculties are obviated .yrhenj this call, thelinender huntinglor this eallingline iwilljwhen 4'it reaches. the slee A lis'h'ed aritonfiatiev Iconriectionf` Y Station to central 'oce. connection Wi W111i' new assume inerti aeafii 'isinitiated by station AifQr 'a statio'rirealcheill thrcual aV i's uifrcierit; operatei'the so-ealledy B relay |5201 efV the' loiv voltage 'psiiiye vbattery 1 (and, es "Y alla fk'y* 14j. thereby 'erarialirfa'the` @Der ator' ane'mergenoytobreak'rinen anffestala-j f thee line lamp'.

nerglthereby closing its contacts.' 2. to "light'th'e Y answers as previously-described by inserting fthe Y,

answeingplug in Jael: 5: whereupon relays .6 and Y'I'fthe cord-sleeve operatein series lwith the cutoff relay 8 of the line. .Relay 8 -di's'- connects the lire relay Operation of relay 6 performs nouseful function at this time but relay 'I closes the circuit of relayv II). which -opensitscontacts II, thereby preventing Arelay I2 Vfrom operating andati-ts rcoritactsl closesthe tip'conductor of Ythev cordv throiighto ground in series with theright-hand lwinding or answering supervisory relayY I4; and the upperwindingof relay I5.` Relay IBv in oper- I atingf'alsvo `closes,'atitsfcontacts ISI, a short cireuit-for relay' thereby releasing and V reduc- -ing th` e 'resistance of' the sleeve circuit. Relays I4 and I5 operate'in serieswiththe subscribers line-and station. Operation of Qrelafy I 4 opens at which'lrelay extinguishes fanotherpointthe'circuit of the'answering super-4 visory lamp I6 which circuit wafspartiallylclosed tip-ofplugm tothe sleeve 'ci the jack and, as-

jack Vwhereupon relay 1I 22 `partially operates from battery on Vthe ring of the cordjna circuit from `b`atteryfresistance |45, contacts ,|44 of relaylZI,

|26 andflower winding of'relayiIZZjgto ground.

vltelay I ZZis partially energized irl-this vcircuitjancl -clojsesfitsoontacts' I2?? to complete the sleeve" cir- 'suit andpperate relay 4"|28 which operates in series'with'-relays I9 and 25fand-.1the low voltage positive battery B I ofthecord-* Relayfl 28,V and resistance inA series therewith, are `of sucha high combined resistance, ihowe/er,` thatjrelay 2 0, whi,ch is ofjrelatively' lowgresista'nce and hence j Y marginal, does not operate in this circuit` Relay |9,however,; operates to energize relay 2| Awhich Y relay;in operating,' wlf1ile relay 2 I'|, li s` released, "close` s a circuit to`I operate m1215544.`V 1 Relaylj |28r n ring-conductor'ofthe cord andtrunk,v contacts closes itsA 'contacts'therebyfully Aoperating 'relay y vfligby1';olnire'cting its upper andlower windings ff' -in serieslbetween *batteryfandground. Complete ductor, operates inA series with the subscribers thel battery of relay |119.

Operationof relay 44 disconnects battery feed relaysfIS and 46 from thecord but relayvl4relV riiainsoperated;v 1 j trunk' ycircuit between the gbattery `and f .ground iat rrelay |119,V andthe subscribers station,

cannow be traced from 'battery, contacts; I55j'of E Y relayl|1513;cont a cts"` |5 3.of relay |22', ring Spring of'ltheffjackIZEfand rin'gjconductor' of the plug 22', contacts of keys 13, "33fand 14, contacts |58 of relay 44, conductor '|59', c'ontacts VII of key relay 44;v contacts of keys 14, 33v and '13, contacts [station inparallel with'impedanceV bridge |33 "and and Vground atvcontacts |54 and |55 Y |64 Aof relay 22, contactsrlofrelay; 2|; tipici"l the plug and jack,'tip ofthe trunk contacts |52 of' relay'IZZ; winding of relay |56,V andjcontacts |54 of relay IUS to ground. c

vImpedance coil "I33. is now connected inbfridge' 'Y' o f the tip and'fring'of thecord between supergA Y visoryvrelayv I4 at'th'e batteryin alcircuitgwhiho." Y'

can be traced Vfrom point |65'i`n the tiprcodil'cf-vV torVcontactsgI of relay 22; contacts-|61 otreshown)l .to battery. *'Atlthisftime'jtle ti ductor is open'at'thecentral oilceff, f

When the i operator answers c' grou'nd` 'will' j be connected'to tl1e"tip,o f the trunkthereby operi-r,"Y atinglrelay |55 in avcircuit including contacts.; 'I 'IS of relay |51, i:or'1 t'acts .I 'I 4of relayl |;2, a'n d l resistance |08.v Relay U15-operates relay l 0 9j" which l*closes ther'trunl; through'totlle` central foiliceA and disconnects ground-and `battery at its Y etacts '5i-M5155 vrRelay'llllelso closesltsaj i lower-most contacts to operate relayY|I 2whic :h lx1A U turn clcsesitscontacts- |15 to lock relay IIIB.l ope (f1. In a coinmonfv batteryv telephone systerrnga manual switchboard, an;automatig-exchange; j manual Vand d ial-sulzvscribersV linesiappearlnggln Vmultiple;jacks ofgthe switchboard*apredeteny T mined vnegative potential sourcev connected to the*- sleevejterminals of. saidf jacks,` vs aidgdia'l` lines` also I appearing in automatic'switchels .atesad exchange 5;" which switches :connect ground tdthefassociated.' c multiple Vjack'sleeve'` whenfa line isseizedthere- Y by, a cord'circuit at'said Switchboardafor; con-vr necting tosaid lines* a.v sleevey circuitin: each endA iofy the cord including-means for' conditioning said'V cordy to conversation responsivegtoconnection 'of 1 either endof the 'cordto any :idle onerofsald' 'Y lines, .and other'meansin eachrcordjsleeve t'o f f ecausesaid cord-to beconditioned for conversar,

tion `when said cordlis' Ycon'netzted Ltoja dia l"11n'e` whosesleeve-circuitisatgroundpotential@ t 2. -In .1a common Ibattery'ftelephone'system; y a j manual switchboard, anvvautomaticfexchange;`

manual and dial. jsubscribersvjlines appearingin 'I multiple jacks of theswitchboard, a'predeter-,be mined negativefpotential vsource connecteditothe f sleeve terminalsof saidjacks, said dial linesalso Y Y vappearing in vautomatic switchesl at'said exchange I whichswitchesconnectJground to the associatedf e multiplerjack sleeves when la line Vis seizedfthere-v 'Aby, *a.cordcircuit'atsaid vswitchboard for con-Y 'c crdgfor conversation responsive to 'connection' of either endgof the c'orcl to any idleofne of; lines; and otherA means in eachcord sleeveftof 'cause said/ cord to be conditioned'fo'rconversationwhen'l said cord is'conneted torr 'alcuylsyrone'v 'ofsaicllinesr v l1 Yrl` "L3-Illia cpmmqn battery: telephone; Systeme 33, 'conductorrIL left winding. of re1ay';sl'4,"and -,@manualiswitchboard, an' automatic ie'xchang'e', fthence over the rin'gof-.the callingnlinalbackover the'itip'bf the line, throughtheright winding of 'reletyfl42.v contacts IGZ-'ffky 33, Contacts v163 01v `manua11a`end dialfsub'sribers,linesappearinglin multiple" iaksz ,ofithje' switehtoa rc1,H aprdeer; f

VAfrnine'dnegative potentiallsourceconnectedtqthe f c sleev'eterminals ofsaid'jacks, said dial unes'also y.

` appearing in automatic switcheslat said exchange which switches connect ground tothe associated multiplejack sleeves when a line is seized thereby, a cord circuit at saids'witchboard for con-V4 necting toY said lines, a sleeve circuit at each end VVVof the cord including relay means for conditioning said cord for conversation responsive to con-A t nection of the cord toa jack whose sleeve is at and said predetermined negative potential, means comprising a source 'of' direct current in 1 series with said sleeve relayv means, and in a series-aiding direction with respectto said negative potential source whenthe 'cord is connected to a line, to insureconditioning :of said cord forV conversation-when'it is connected to a jaclgwhose sleeveis atrground potential. if i Y 4. In `a common battery telephone system, a

*of each of said cords, and meansA in said sleeve Vcircuitsfor conditioning a cord forconversation fr in one manner i'lf one subscribers line is calling, and the called -line if another subscribers line,

and in different manners depending `on whether e thcallingline is of saideother type andthe called v line is a subscriber, or whether a subscribers line manual switchboard, manual v,and dial subscribj ers lines, multiple jacks at said switchboard ter.-

Y minatingsaid subscriberslines, a source ofpredeterminedrnegative potential connected to the' sleeveV terminals offsaid jack, cord circuits at said switchboard forl connecting to said lines, a.

sleeve circuit inieach end of each cord, and means in each sleeve circuit for conditioningY anyV cord forconversation responsive toconnection of eitherend to any one of saidV lines regardless.

of its busy condition.

5. Inra common battery telephone system, a

manual switchboard, vmanual andV dial subscribers lines, multiple jacks` at said switchboard terminating said, subscribers: lines, a source of predetermined negative" potential Yconnected to' the sleeve terminals of said jacks, Vcord circuits at Vsaid switchboard for connecting to said lines,

` a sleeve circuitin each end of each cord, and

means in each sleeve circuit for conditioning any cord for conversation responsive to connectiony of either end thereof to any one of'said lines regardless of itsbusy-oridle condition, saidineans including a source ofl direct current*oixpredeter` mined low potential in series-raiding relation .to said negative potentialsource connected to the is calling and the called'lineis of said other type,

vsaid sleeve'means being effective to condition saidV cordlfor conversation in the'proper manner re- 'lgardless of the busy condition Vf 'the' called line. 8. Ina commonbattery telephone system, a

manual switchboard, an4 automatic exchange,

manual andldial` subscribers linesv appearing in A multiplejacks `at the switchboard whose sleeve terminals'` have: a predetermined 'resistance connectionrto negative battery,fsaid dial lines also l V @appearing in automatic switches ,Pat said ex- Y change `which switches `connect ground to-the associated multiple `jack sleeves wheny a line Vis' seized thereby, other lineshaving-jackappearances at said'switchboardfwhose normal sleeve 7 conditions diierfroml that of said subscribers" lines, a cord circuit'at said switchboard for interconnecting said lines having answering and call- `ing ends, a sleeve-circuit in each end of saidcord,

relay means in each sleeve circuit responsive to the interconnection in either direction of 4any two idle subscribers lines to condition said cord inV one manner for conversation, in another manner for conversation responsive tdconnection of the answering cord to a "callingone offsaid 'other linesand Vthe callingrcord to an idleironerof saidA subscribers lines,` and in a `third manner when the answering cord is connected to a callingfsubscribers line and the callingcord to an idle one of `said other lines, and means `toenable said cord tocondition itself for conversation in the proper manner when either fend of the oord is connected to `a dial line jack whose sleeve terminal istat ground'potential, said latter means insleeve'of the jack to which the cord-isconnected.` 'l

6. In a telephone system, lines ofl two diierent characters, a cordcircuit for interconnecting a calling with a called one of said lines, :means associated withsaid cord circuit responsive tothe i interconnection of two lines'ofpne Vcharacter by thel cord for converting said cord into afbridged impedance battery feed type of cord,'and means associated with said cord circuit responsive to the interconnectionof two lines of Y different Ycharacter for converting said cord to receive its battery v feed from one'y of said lines, and other means, associated' with the cord for'effe'cting'- said conver` sion regardlessv of the busyV condition of the called line. f

'7. In a telephone system, a.' manual switchboard, subscribers lines terminatingV thereat in multiple jacks, a source of negativefpotential cluding an individuali-low voltage positiveV battery inseries with each cord sleeve circuit.

9L In a telephone system, a switchboard, rst

' and secondY groups of Vlines `of ldifferent charac- 'etersv terminating thereat in multiple `jacks the sleeve terminals of which are at a predetermined potential-withA respect to ground whenY therespective linesare idle, andrat a different poten- `ctial"when lousy, a cord circuit for interconnecting two Vlines of the first-group, ,or a line o f the iirst group with a, line ofthe second group, meansrre- "the viirst group'to condition said cordcircuit inV connected to all the` sleeves of said-jacks, lines of 1 other types also appearing in jacks atsaid switchboard and having sleeve potential characteristics diiering from said subscribers 'vlinelsfcord circuits at said switchboard forinterconnecting any.

two subscribers lines or a subscribers lineand aV line of said other type, a sleeve circuitin each end sponsive tothe interconnection of two lines in one manner, vresponsive to connectionof a line i in the` `first group with'a line in the second group in onei direction through the cord in another i manner, and -in `the opposite'direction through the cordA ina third manner, all regardless of the Y busy condition of the called line, said means comprising a Ysleeve circuit at each end of the cord seriallyincluding arlsensitive and a marginal re- Y r ,lay and an auxiliary source of direct current whose potential differs materially from'the idle l potential'cfthe sleeve of the connected line."

Y M. BAscoM.; y'

VFREDERICK a. LAMBERTY. Y 

